Protective system for electric meters



Nov. 5, 1935.

H. D. MORTON PROTECTIVE SYSTEM FOR ELECTRIC METERS Fiied Oct. 20, 1953INVENTOR ATTORNEYS Patented Nov. 5, 1935 UNITED STATES PROTECTIVE SYSTEMFOR ELECTRIC METERS Harry D. Morton, New York, N. Y., assignor toWilliam 0. Canfield, trustee Application October 20, 1933, Serial No.694,391

5 Claims.

It is customary in supplying electrical energy to a consumer, to runsupply wires from a relatively inaccessible'point at the main supplylines (as for example from the top of a pole) into the consumerspremises, and to fix the meter at an accessible point on the consumerspremises. The very accessibility of this meter frequently leads tosubstantial losses to the electric light companies, as consumers canreadily by-pass or jump the meter and carry the electrical energy intotheir service lines "without the consumption of this energy beingrecorded.

The present invention relates to a structure whereby an apparatus ispositioned at a relatively inaccessible point (as for example atthepoint 7 where the consumers service lines are connected to the mainsupply lines) and this apparatus is connectedto a device within themeter, the whole being so constructed that if the electrical energypassing into'the meter is less than the electrical energy withdrawn fromthe main supply lines, then a definite indication of this differencewill be given. Such indication ordinarily will take the form of entirelycutting off the supply of energy, or this energy may be supplied througha high resistance so that only a small amount will be delivered, or itmay be supplied for example through some other device, such as a flasherwhich will interrupt the service periodically. Any such device or resultis intended to be included when reference is made to the fact that thenormal flow of current is interrupted.

In carrying out this invention, some'means is supplied so that thecurrent'leaving the main supply line can be compared with the currententering into the meter. This may be done by the use of resistances andshunt circuits, but with alternating current an equivalent'result can behad by the use of two identical transformers, one of which is positionedat the inaccessible point and the other of which is located within themeter casing. The electrical energy passes through the primaries ofthese transformers and as only a few turns are needed in theseprimaries, the energy consumed will be very small. The secondaries ofthese two transformers are connected to a common point which willordinarily be the inaccessible point, though if desired this point maybe contained in a locked box adjacent the meter. At this point apparatusis supplied, controlled by the two secondary circuits, and thisapparatus is so constructed that if thecurrent in the secondary circuitof the transformer located within the meter falls substantially belowthe current of the other secondary circuit, then the service line willbe broken through the operation of an appropriate switch, or some otherindication will be given as set forth above.

My invention can readily be understood by reference to the accompanyingdrawing, in which 5; Fig. 1 shows diagrammatically'a system applicableeither to direct or alternating current, while Fig. 2 showsdiagrammatically a more complicated but more efiicien-t embodiment ofthe invention which in this particular form is adapt- 10. ed only toalternating current.

Referring now to Fig. 1, the numerals l0 and I2 represent the mains ormain supply lines. Adjacent the point where the supply is drawn from toline H] is a service wire l6 which goes into casing I4 and runs'to oneterminal of the toggle switch l-8. From the toggle switch l8 this lineruns through a resistance 2!] and thence out of the casing M to themeter casing 22. Inside the meter casing 22 the wire I6 is connected toa resistance 24 and thence runs through the usual meter windingsindicated at 26 to the consumers supply as indicated by the lamp- 28.Service wire 30 runs from main supply line l2 into the meter casing 22and may pass through the protective casing I 4 or not as desired.

Wire 32 is connected on the meterside of resistance 24 and runs towinding 34, the opposite end of which is' connected to wire it at anycon- Venient point. A second winding 36 wound in opposition to thewinding 3 is connected to wire It on opposite sides of resistance 20.Resistances 20 and 24 are so balanced with their circuits that undernormal circumstances the same amount of current will flow through coils34 and 36. These coils operate the armature 4E! which in turn isconnected to the toggle switch it and these coils are wound inopposition to each other so that when they are subjected toequal'excitation their effect is neutralized. In the normal operation ofthe device, the switch it is closed and as coils 34 and 36 neutralizeeach other, this switch will remain closed. If, however, the metercasing 22 is by-passed, the amount of current supplied to winding 34will drop off, and thereupon coil 36 will be able to function and willopen toggle switch l8, disconnecting all supply to the premises. Torestore service the electric company will have to open casing l4 andclose switch I8 and of course they will not do this unless the meter 22is functioning properly. In the embodiment shown in Fig. 2, there is aprotective casing 42 and the meter casing is here indicated by thenumeral 44. From the mains l0 these lines is positioned a casing I l.Connected 15 and I2 service lines 46 and 48 run into casing 42 which maybe positioned near the mains l8 and I2.

Connected in series with service line 46 is the primary 50 (which mayconsist of a few turns of the service wire) of a small currenttransformer 52. The secondary 54 of this transformer supplies current toa primary winding 56 of a balanced transformer 58. This balancedtransformer also provided with anotherprimarywindingfifl which is wounddifferentially with reference to the winding 56 so that when equalcurrent is supplied to the windings 58 and 68 there will be no inducedcurrent in the secondary 62.

Current is supplied to winding 60 from the secondary 64 of a thirdtransformer 68, similar to transformer 52, installed in the meter casing44 orin an auxiliary housing permanently attached to the meter casing.The primary 68 of the meter casing transformer 86, like primary 50 oftransformer 52, is connected in series in the service line 46 and likewinding 58 may consist of a few turns of the service wire. 10 indicatesthe series winding and 12 the potential winding of the meter. The loadcircuit is here indicated, as in the previous instance, as connected tothe lamp 28. It is intended that transformers 52 and 68 shall be ofidentical design and construction, and the circuits which include theirsecondary windings are initially so adjusted as to resistance andimpedance that the magnitude of their respective current outputs is thesame, and so that their currents are in phase. Transformer windings 56and 60 being identical but oppositely wound, it follows that so long asall the current flowing through primary winding 58 also flows throughprimary winding 88, a condition of equilibrium obtains in thetransformer 58 and there is no output from the secondary winding 62.

The secondary winding 82 of transformer 58 is here shown as connected toa resistance heating element 14, the terminals of which are fused in thewalls of one branch of the hermetically sealed U-shaped glass tube 16.In the lower portion of this tube is a mass of mercury indicated at 18,immersed in which is a terminal 80 fused in the wall of the glass tube16 near the bottom thereof and connected to service line 48. Fused inthe wall of the U-tube 16 at a position above the level of the mercuryI8 and in the opposite arm from the heater element 14 is a terminal 82connected by a line 84 to one terminal of an electromagneticallyoperated switch or relay 86, the other terminal of which is connected tothe service line 46. The relay 86 operates a switch interposed in theservice line 46, but I find it desirable to interpose a fuse asindicated at 88 which is shunted across the terminals of this switch.

From this construction it will be seen that if the current flowing intothe primary winding 68 of transformer 58 is substantially reduced (aswill be the case if one jumps or by-passes the meter 44) an electricalflow will be set up in secondary 62, which will heat resistance element14 causing the vapor or air in that end of the tube to expand so thatthe mercury rises in the opposite arm of the tube 16 making a contactbetween terminal 80 and terminal 82, thus energizing relay 86 to breakthe circuit, and causing all of the energy Passing through service line46 to pass through the fuse 88 which will quickly burn out. The fuse 88is not essential, but I find it advisable to use the same as it willprevent undue sparking at the relay when the flow of current through themain service line is interrupted. In any event, rregular service cannotbe established until the shunt circuit is removed, the protective casing42 opened and the relay 88 operated manually to close the regularcircuit in supply line 48, and at that time the fuse 88 will bereplaced.

It is to be noted that in each of the constructions shown the energywithdrawn from within the meter housing is used to prevent the devicefrom functioning, so that any attempt to eliminate the control device bycutting the supplemental wires that run from the meter housing willimmediately cause the device to operate. Also due to the fact that abalance must be maintained, if transformer 52 is put on the pole and therest of the control equipment at a convenient place on the consumer'spremises, or included in the meter housing, cutting the wires fromtransformer 52 will serve to operate the device.

What I claim is:

1. In a device of the type described in combination with a source ofelectrical supply and an electric meter, means for withdrawing energyfrom a point within the meter and similar means for withdrawing energyfrom a point in series with the meter and intermediate the meter and thesupply and positioned at a point substantially removed from the meterand relatively inaccessible thereto, and means controlled by therelationship of the energy withdrawn from said points such that if theflow of energy withdrawn from within the meter falls substantially belowthe fiow of energy from said intermediate point or if any connectionbetween such intermediate point and the meter is broken, the supply ofelectricity to the meter will be interrupted.

2. In combination with a source of electrical supply, an electric meterand a load circuit, a transformer substantially enclosed with the meterand having its primary in series with one of the feed lines to themeter, a second transfonner having its primary in series with the firsttransformer but located at a point intermediate the meter and the sourceof supply and having its secondary in a circuit independent of thesecondary of such first transformer, a relay between said supply andsaid load circuit and means controlled by said secondary circuitswhereby said relay will operate to open a connection between theelectrical supply and the load circuit if substantially less energyflows through the primary of one of said transformers than through theprimary of the other of said transformers.

3. In combination with a source of electrical supply, an electric meterand a load circuit, a transformer in the meter casing in series with thesupply to the meter, a second similar transformer having its primary inseries with the meter and supply positioned at a point remote from themeter, opposed coils connected to the secondaries of said transformersbut in electrically independent circuits and a relay in the supply lineto the meter, and means whereby said relay is operated if the current inone of said opposed coils becomes substantially less than the current inthe other of said coils.

4. In combination with a source of electric supply, an electric meterand a load circuit, a transformer substantially enclosed with the meterand having its primary in series with one of the feed lines to themeter,.a second transformer having its primary in series with the firsttransformer but located at a point intermediate the meter and the sourceof supply and having its secondary in a circuit independent of thesecondary of such first transformer, and means controlled by therelationship of the current induced in the secondaries of said twotransformers such that if the flow of current from the secondary of thetransformer substantially enclosed with the meter falls substantiallybelow the flow of current from the secondary of the other transformer,the flow of electricity from the supply tothe load circuit will beinterrupted.

5. In combination with a source of electric supply, an electric meterand a load circuit, a transformer substantially enclosed with the meterand having its primary in series with one of the feed lines to themeter, a second transformer having its primary in series with the firsttransformer but located at a point intermediate the meter and the sourceof supply and having its secondary in a circuit independent of thesecondary of such first transformer, a relay, a fuse in the line betweensaid supply and said load circuit and means controlled by said secondarycircuits, whereby if substantially less energy flows through the primaryof one of said transformers than through the primary of the other ofsaid transformers,

said relay will operate to cause said fuse to be blown.

HARRY D. MORTON.

